smtp_util.c

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/*
 * Utility functions for the Citadel SMTP implementation
 *
 * Copyright (c) 1998-2021 by the citadel.org team
 *
 * This program is open source software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
 
#include "sysdep.h"
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <termios.h>
#include <fcntl.h>
#include <signal.h>
#include <pwd.h>
#include <errno.h>
#include <sys/types.h>
#include <syslog.h>
#include <time.h>
#include <sys/wait.h>
#include <ctype.h>
#include <string.h>
#include <limits.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <libcitadel.h>
#include "citadel.h"
#include "server.h"
#include "citserver.h"
#include "support.h"
#include "config.h"
#include "control.h"
#include "user_ops.h"
#include "database.h"
#include "msgbase.h"
#include "internet_addressing.h"
#include "genstamp.h"
#include "domain.h"
#include "clientsocket.h"
#include "locate_host.h"
#include "citadel_dirs.h"
#include "ctdl_module.h"
#include "smtp_util.h"
 
const char *smtp_get_Recipients(void) {
    struct citsmtp *sSMTP = SMTP;
 
    if (sSMTP == NULL)
        return NULL;
    else return ChrPtr(sSMTP->from);
}
 
 
/*
 * smtp_do_bounce() is caled by smtp_process_one_msg() to scan a set of delivery
 * instructions for errors and produce/deliver a "bounce" message (delivery
 * status notification).
 *
 * is_final should be set to:
 *  SDB_BOUNCE_FATALS   Advise the sender of all 5XX (permanent failures)
 *  SDB_BOUNCE_ALL      Advise the sender that all deliveries have failed and will not be retried
 *  SDB_WARN        Warn the sender about all 4XX transient delays
 */
void smtp_do_bounce(const char *instr, int is_final) {
    int i;
    int lines;
    int status;
    char buf[1024];
    char key[1024];
    char addr[1024];
    char dsn[1024];
    char bounceto[1024];
    StrBuf *boundary;
    int num_bounces = 0;
    int bounce_this = 0;
    struct CtdlMessage *bmsg = NULL;
    struct recptypes *valid;
    int successful_bounce = 0;
    static int seq = 0;
    StrBuf *BounceMB;
    long omsgid = (-1);
 
    syslog(LOG_DEBUG, "smtp_do_bounce() called");
    strcpy(bounceto, "");
    boundary = NewStrBufPlain(HKEY("=_Citadel_Multipart_"));
 
    StrBufAppendPrintf(boundary, "%s_%04x%04x", CtdlGetConfigStr("c_fqdn"), getpid(), ++seq);
 
    /* Start building our bounce message */
 
    bmsg = (struct CtdlMessage *) malloc(sizeof(struct CtdlMessage));
    if (bmsg == NULL) return;
    memset(bmsg, 0, sizeof(struct CtdlMessage));
    BounceMB = NewStrBufPlain(NULL, 1024);
 
    bmsg->cm_magic = CTDLMESSAGE_MAGIC;
    bmsg->cm_anon_type = MES_NORMAL;
    bmsg->cm_format_type = FMT_RFC822;
    CM_SetField(bmsg, eAuthor, HKEY("Citadel"));
    CM_SetField(bmsg, eOriginalRoom, HKEY(MAILROOM));
    CM_SetField(bmsg, eMsgSubject, HKEY("Delivery Status Notification (Failure)"));
    StrBufAppendBufPlain(BounceMB, HKEY("Content-type: multipart/mixed; boundary=\""), 0);
    StrBufAppendBuf(BounceMB, boundary, 0);
    StrBufAppendBufPlain(BounceMB, HKEY("\"\r\n"), 0);
    StrBufAppendBufPlain(BounceMB, HKEY("MIME-Version: 1.0\r\n"), 0);
    StrBufAppendBufPlain(BounceMB, HKEY("X-Mailer: " CITADEL "\r\n"), 0);
    StrBufAppendBufPlain(BounceMB, HKEY("\r\nThis is a multipart message in MIME format.\r\n\r\n"), 0);
    StrBufAppendBufPlain(BounceMB, HKEY("--"), 0);
    StrBufAppendBuf(BounceMB, boundary, 0);
    StrBufAppendBufPlain(BounceMB, HKEY("\r\n"), 0);
    StrBufAppendBufPlain(BounceMB, HKEY("Content-type: text/plain\r\n\r\n"), 0);
 
    if (is_final == SDB_BOUNCE_ALL) {
        StrBufAppendBufPlain(
            BounceMB,
            HKEY(   "A message you sent could not be delivered "
                "to some or all of its recipients\ndue to "
                "prolonged unavailability of its destination(s).\n"
                "Giving up on the following addresses:\n\n"),
            0);
    }
    else if (is_final == SDB_BOUNCE_FATALS) {
        StrBufAppendBufPlain(
            BounceMB,
            HKEY(   "A message you sent could not be delivered "
                "to some or all of its recipients.\n"
                "The following addresses were undeliverable:\n\n"),
            0);
    }
    else if (is_final == SDB_WARN) {
        StrBufAppendBufPlain(
            BounceMB,
            HKEY("A message you sent has not been delivered "
                "to some or all of its recipients.\n"
                "Citadel will continue attempting delivery for five days.\n"
                "The following addresses were undeliverable:\n\n"),
            0);
    }
    else {  // should never get here
        StrBufAppendBufPlain(BounceMB, HKEY("This message should never occur.\n\n"), 0);
    }
 
    /*
     * Now go through the instructions checking for stuff.
     */
    lines = num_tokens(instr, '\n');
    for (i=0; i<lines; ++i) {
        long addrlen;
        long dsnlen;
        extract_token(buf, instr, i, '\n', sizeof buf);
        extract_token(key, buf, 0, '|', sizeof key);
        addrlen = extract_token(addr, buf, 1, '|', sizeof addr);
        status = extract_int(buf, 2);
        dsnlen = extract_token(dsn, buf, 3, '|', sizeof dsn);
        bounce_this = 0;
 
        syslog(LOG_DEBUG, "key=<%s> addr=<%s> status=%d dsn=<%s>", key, addr, status, dsn);
 
        if (!strcasecmp(key, "bounceto")) {
            strcpy(bounceto, addr);
        }
 
        if (!strcasecmp(key, "msgid")) {
            omsgid = atol(addr);
        }
 
        if (!strcasecmp(key, "remote")) {
            if ((is_final == SDB_BOUNCE_FATALS) && (status == 5)) bounce_this = 1;
            if ((is_final == SDB_BOUNCE_ALL) && (status != 2)) bounce_this = 1;
            if ((is_final == SDB_WARN) && (status == 4)) bounce_this = 1;
        }
 
        if (bounce_this) {
            ++num_bounces;
            StrBufAppendBufPlain(BounceMB, addr, addrlen, 0);
            StrBufAppendBufPlain(BounceMB, HKEY(": "), 0);
            StrBufAppendBufPlain(BounceMB, dsn, dsnlen, 0);
            StrBufAppendBufPlain(BounceMB, HKEY("\r\n"), 0);
        }
    }
 
    /* Attach the original message */
    if (omsgid >= 0) {
        StrBufAppendBufPlain(BounceMB, HKEY("--"), 0);
        StrBufAppendBuf(BounceMB, boundary, 0);
        StrBufAppendBufPlain(BounceMB, HKEY("\r\n"), 0);
        StrBufAppendBufPlain(BounceMB, HKEY("Content-type: message/rfc822\r\n"), 0);
        StrBufAppendBufPlain(BounceMB, HKEY("Content-Transfer-Encoding: 7bit\r\n"), 0);
        StrBufAppendBufPlain(BounceMB, HKEY("Content-Disposition: inline\r\n"), 0);
        StrBufAppendBufPlain(BounceMB, HKEY("\r\n"), 0);
 
        CC->redirect_buffer = NewStrBufPlain(NULL, SIZ);
        CtdlOutputMsg(omsgid,
            MT_RFC822,
            HEADERS_ALL,
            0, 1, NULL, 0,
            NULL, NULL, NULL
        );
        StrBufAppendBuf(BounceMB, CC->redirect_buffer, 0);
        FreeStrBuf(&CC->redirect_buffer);
    }
 
    /* Close the multipart MIME scope */
    StrBufAppendBufPlain(BounceMB, HKEY("--"), 0);
    StrBufAppendBuf(BounceMB, boundary, 0);
    StrBufAppendBufPlain(BounceMB, HKEY("--\r\n"), 0);
    CM_SetAsFieldSB(bmsg, eMesageText, &BounceMB);
 
    /* Deliver the bounce if there's anything worth mentioning */
    syslog(LOG_DEBUG, "num_bounces = %d", num_bounces);
    if (num_bounces > 0) {
 
        /* First try the user who sent the message */
        if (IsEmptyStr(bounceto)) {
            syslog(LOG_ERR, "No bounce address specified");
        }
        else {
            syslog(LOG_DEBUG, "bounce to user <%s>", bounceto);
        }
        /* Can we deliver the bounce to the original sender? */
        valid = validate_recipients(bounceto, smtp_get_Recipients (), 0);
        if (valid != NULL) {
            if (valid->num_error == 0) {
                CtdlSubmitMsg(bmsg, valid, "");
                successful_bounce = 1;
            }
        }
 
        /* If not, post it in the Aide> room */
        if (successful_bounce == 0) {
            CtdlSubmitMsg(bmsg, NULL, CtdlGetConfigStr("c_aideroom"));
        }
 
        /* Free up the memory we used */
        if (valid != NULL) {
            free_recipients(valid);
        }
    }
    FreeStrBuf(&boundary);
    CM_Free(bmsg);
    syslog(LOG_DEBUG, "Done processing bounces");
}
 
 
char *smtpcodes[][2] = {
    { "211 - System status / system help reply" },
    { "214", "Help message" },
    { "220", "Domain service ready" },
    { "221", "Domain service closing transmission channel" },
    { "250", "Requested mail action completed and OK" },
    { "251", "Not Local User, forward email to forward path" },
    { "252", "Cannot Verify user, will attempt delivery later" },
    { "253", "Pending messages for node started" },
    { "354", "Start mail input; end with ." },
    { "355", "Octet-offset is the transaction offset" },
    { "421", "Domain service not available, closing transmission channel" },
    { "432", "Domain service not available, closing transmission channel" },
    { "450", "Requested mail action not taken: mailbox unavailable. request refused" },
    { "451", "Requested action aborted: local error in processing Request is unable to be processed, try again" },
    { "452", "Requested action not taken: insufficient system storage" },
    { "453", "No mail" },
    { "454", "TLS not available due to temporary reason. Encryption required for requested authentication mechanism" },
    { "458", "Unable to queue messages for node" },
    { "459", "Node not allowed: reason" },
    { "500", "Syntax error, command unrecognized" },
    { "501", "Syntax error in parameters or arguments" },
    { "502", "Command not implemented" },
    { "503", "Bad sequence of commands" },
    { "504", "Command parameter not implemented" },
    { "510", "Check the recipient address" },
    { "512", "Domain can not be found. Unknown host." },
    { "515", "Destination mailbox address invalid" },
    { "517", "Problem with senders mail attribute, check properties" },
    { "521", "Domain does not accept mail" },
    { "522", "Recipient has exceeded mailbox limit" },
    { "523", "Server limit exceeded. Message too large" },
    { "530", "Access Denied. Authentication required" },
    { "531", "Mail system Full" },
    { "533", "Remote server has insufficient disk space to hold email" },
    { "534", "Authentication mechanism is too weak. Message too big" },
    { "535", "Multiple servers using same IP. Required Authentication" },
    { "538", "Encryption required for requested authentication mechanism" },
    { "540", "Email address has no DNS Server" },
    { "541", "No response from host" },
    { "542", "Bad Connection" },
    { "543", "Routing server failure. No available route" },
    { "546", "Email looping" },
    { "547", "Delivery time-out" },
    { "550", "Requested action not taken: mailbox unavailable or relaying denied" },
    { "551", "User not local; please try forward path" },
    { "552", "Requested mail action aborted: exceeded storage allocation" },
    { "553", "Requested action not taken: mailbox name not allowed" },
    { "554", "Transaction failed" }
};
 
 
char *smtpstatus(int code) {
    int i;
 
    for (i=0; i<(sizeof(smtpcodes)/sizeof(char *)/2); ++i) {
        if (atoi(smtpcodes[i][0]) == code) {
            return(smtpcodes[i][1]);
        }
    }
    
    return("Unknown or other SMTP status");
}